Scotland is bracing for an influx of fortune seekers after a gold-panning enthusiast found an 85.7-gram nugget lying in a river bed. It’s believed to be the largest nugget ever found in Britain and the discovery has set off a flurry of interest among gold bugs.

“My phone has been ringing off the hook,” said Leon Kirk, who sells gold-panning equipment in Glasgow and knows the man who found the nugget. “To get something that’s nearly 86 grams is massive for this country.”

Mr. Kirk said the man, dubbed “Mr. Lucky,” wants to remain anonymous and won’t reveal where he found the treasure, which is believed to be worth more than £50,000 ($85,900). He’s had it for more than a year but was too afraid to come forward until now.

“He slowly got more confident and he approached me for advice,” said Mr. Kirk, who urged him to make the finding public. Mr. Kirk has had a chance to examine the nugget, which he described as “off the Richter scale” for gold panning. “To hold it was very nice but to drop it into the palm of your hand was unbelievable,” he said. “You wouldn’t believe how heavy it feels.”

Gold is a rare commodity in Scotland and there hasn’t been any significant gold-mining activity in about 400 years. That’s beginning to change as more deposits are discovered and gold panning becomes an increasingly popular hobby.